Re: [PATCH v5 10/13] ARM: KVM: Guest wait-for-interrupts (WFI) support

[Avi Kivity <avi@redhat.com>]

On 12/12/2011 06:20 PM, Christoffer Dall wrote:
> >>
> >> +/**
> >> + * kvm_handle_wfi - handle a wait-for-interrupts instruction executed by a guest
> >> + * @vcpu:    the vcpu pointer
> >> + * @run:     the kvm_run structure pointer
> >> + *
> >> + * Simply sets the wait_for_interrupts flag on the vcpu structure, which will
> >> + * halt execution of world-switches and schedule other host processes until
> >> + * there is an incoming IRQ or FIQ to the VM.
> >> + */
> >>  int kvm_handle_wfi(struct kvm_vcpu *vcpu, struct kvm_run *run)
> >>  {
> >> +     trace_kvm_wfi(vcpu->arch.regs.pc);
> >> +     if (!vcpu->arch.virt_irq)
> >> +             vcpu->arch.wait_for_interrupts = 1;
> >
> > Why not just block here?
> >
>
> well, if we block, but receive a signal that we want to go back into
> userspace for, and then come back but the guest should still be
> waiting, then I want that flag set, and I think it's the most logical
> control flow. Am I missing something completely?

That's just not the flow that the other archs use, I don't think that it
really matters.  kvm_vcpu_block() checks for and wakes up on signals, so
it's okay to call it from here directly.

-- 
error compiling committee.c: too many arguments to function